Discoveries concerning the development of congenital heart defects and gene-based therapies are of major importance for the future of Pediatric Cardiology. However, at present there is a severe shortage of researchers concerned with these issues, and more importantly, there are few institutions where appropriate research training is available. Our proposed program will fill this need. The pediatric cardiology research fellowship at the Children's Hospital of Philadelphia (CHOP) will train physician scientists and basic researchers to break new ground concerning the genetic basis of congenital heart disease and its mechanistic based therapy. Our program has several key features that can enable this goal: Pediatric Cardiology at CHOP is the site of one of two NIH SCOR programs in molecular cardiac development. Furthermore, our training program will have the full involvement of the Institute for Human Gene Therapy at the University of Pennsylvania, as a training site. We will also bring together trainers both from CHOP and mentors representing a broad base of cardiovascular oriented academic units at Penn, including: The Institute for Medicine and Engineering, the Center for Experimental Therapeutics, and the Division of Cardiology at the Hospital of the University of Pennsylvania. We will establish three major interactive areas of research: 1) Experimental pharmacology and gene therapy; 2) Cardiovascular molecular genetics and development; and 3) Cardiovascular pathophysiology. Our trainers are all leaders of basic investigative efforts in these areas. In addition to our laboratory efforts, we also proposed to provide an opportunity for training in outcomes research. This arm of our program will train leaders who can evaluate the effects of molecular therapeutic approaches to treating heart disease in the young. We have already recruited into CHOP a core group of entry level pediatric cardiology clinical trainees, who are well suited research candidates for our first year of support on this Institutional national Research Service Award Program. Graduates of our program will provide leadership in the field at leading academic institutions. They will exert a major influence in improving the treatment of heart diseases in the young through state-of- the-art research endeavors.